Non-invasive imaging technologies allow images of the internal structures or features of a patient to be obtained without performing an invasive procedure on the patient. In particular, such non-invasive imaging technologies rely on various physical principles, such as the differential transmission of X-rays through the target volume or the reflection of acoustic waves, to acquire data and to construct images or otherwise represent the observed internal features of the patient.
For example, in computed tomography (CT) and other X-ray based imaging technologies, X-ray radiation spans a subject of interest, such as a human patient, and a portion of the radiation impacts a detector where the image data is collected. In digital X-ray systems a photodetector produces signals representative of the amount or intensity of radiation impacting discrete pixel regions of a detector surface. The signals may then be processed to generate an image that may be displayed for review. In CT systems a detector array, including a series of detector elements, produces similar signals through various positions as a gantry is displaced around a patient.
In the images produced by such systems, it may be possible to identify and examine the internal structures and organs within a patient's body. However, the produced images may also include artifacts that adversely affect the quality of the images due to a variety of factors. For example, these factors may include beam hardening for non-water materials, heel-effect related spectral variation in wide cone CT systems, bone induced spectral (BIS) due to detection variation of different detector pixels coupled to spectral changes attenuated by bone or other non-water materials, and other factors. Present techniques to correct for these artifacts are empirically based and inaccurate.